Iran released a French embassy employee on August 11 but still kept detaining a young French academic, who are both on charges related to post-election protests in Iran, French President Nicolas Sarkozy's office said in a statement.
The statement said that Sarkozy spoke to Nazak Afshar via telephone after the French-Iranian staff was freed from prison.
Sarkozy also called on a rapid release of the French academic Clotilde Reiss, 24, who is accused of spying.
Reiss and Afshar were among defendants on charges related to protests in Iran after disputed presidential election in June.
Sarkozy expressed his "gratitude to the countries of the European Union and to other friendly states, such as Syria, who gave us their support in this first phase."
Earlier on Tuesday, the French government spokesman Luc Chatel said France was hoping Reiss to be released early.
"Clotilde Reiss is innocent and the victim of a sham trial," Chatel said. "We have demanded and will continue to demand her release."
Iran's ambassador Seyed Mehdi Miraboutalebi said earlier Tuesday that Iran has offered to let Reiss stay in French embassy during the trial.
